2019-01-012024-05-13https://scholars.lib.ntu.edu.tw/handle/123456789/651785摘要：非飽和層在地球關鍵層(Earth’s Critical Zone)分層中，扮演連結地表植披與地下水飽和層的角色。 在非飽和層中的孔隙水(pore water)，多半以殘留水(resident water)或者是殘餘水(residual water) 的狀態存在(舊水)。非飽和層的舊水一方面影響了”新水“(降雨、灌溉、滲漏等)入滲的分布型態 (pattern)，也透過與新水的互動影響地下水與河川水質。近期研究顯示植物所使用的土壤水(resident water)，並不會與流入地下水與河川的新水(incoming water)充分混合，稱之為 dynamic partial mixing 或是 ecohyrologic separation。此現象應與孔隙尺度的土壤水毛細封存(capillary trapping)以及土壤水蒸 發過程相關。本研究計畫以孔隙、達&#11972;、與現地尺度的實驗與模擬，探討非飽和土壤中，空氣、新水 與舊水的互動機制，驗證與解釋 ecohyrologic separation 假設與物理機制。第一階段計畫擬三年時間 進行，第一年以過往科技部計畫成果為基礎，利用微模型實驗觀測新舊水互動，以及舊水蒸發對互動 情形的影響。同時利用數值模式模擬新舊水互動。第二年採用沙柱入滲實驗，以雙相流模式 Buckley-Leverett theory 為基礎進行實驗分析與解釋。第三年則整合年兩年研究成果，進行現地實驗。 期望透過一系列實驗，釐清舊水的蒸發過程在這互動所扮演的角色。初始研究成果將有助於了解非飽 和層水分移動過程，溶質的傳輸機制，希望能凸顯非飽和層土壤與水文地質條件對於整體的水循環的 重要性。未來逐步利用相同的技術探討孔隙介質多相流初始殘餘相對於毛細封存效率的影響(第二階 段)，以及地表植物與生地化過程對於新舊水互動與毛細封存效率的影響(第三階段)。最後期望研究 成果將能應用於農業施肥與灌溉、地下氣、液體分佈模擬、地下水污染整治以及地質碳封存等工程議題。<br> Abstract: Vadose zone connects the surface pedosphere and saturated groundwater zone in Earth`s Critical Zone. Resident water (old water) in the Vadose zone not only affects the infiltration pattern of new water (rainfall infiltration, irrigation, leakage, etc.) but also influences the water quality of groundwater and stream. Recent studies found that the new-old water interplay effects the neutral intake of vegetation, and evaporation seems to be the key in this interplay. Plants use soil water that does not well mixed with the water contributing to groundwater recharge or steam flow. It is called dynamic partial mixing or ecohydrologic separation. Researchers proposed a hypothesis that the ecohydrologic separation is strongly related to the pore-scale new-old water interplay. However, no systematic investigation has been done to understand and describing the phenomenon by performing pore-scale experiments and modeling. The main propose of this study is to study mechanisms of new-old water interplay from pore scale to field scale. We proposed a three-year research project. Based on the results of our previous MOST projects, in the first year, we will perform micromodel experiments and numerical modelling to observe and simulate the new-old water interplay. In the second year, downward infiltration experiments in sand columns will be performed. The result will be analyzed and interpreted based on the two-phase flow model, Buckley-Leverett theory. In-situ experiments will be processed based on the results from the past two years. In the end, we expect to better understand not only the role of evaporation on the interplay between new water and old but also the importance of the soil and geohydrology to the hydrological cycle. Our study result will benefit the agricultural water usage, subsurface water monitoring, groundwater remediation, and even geological carbon sequestration.動態混合新舊水地球關鍵層dynamic mixingold-new watercritical zone